Sedimentation is important in many processes for example in cement, chemical and food industries. Investigation of the sedimentation process of solid bodies showed a phenomenon as settling velocity is not the constant value as it is expected from the analytical deduction; rather it has fluctuating behaviour. Seeking an explanation, detailed two phase hydrodynamic models are developed. In the present work, two-dimensional incompressible flow equation in conservative Euler form is solved numerically on PC by an implicit finite difference method, and the fluid-solid interaction is described by the Immersed Boundary Method. For additional model validation, Particle Tracing module of COMSOL is applied as well. The self-developed simulator based on an a priori (white box) model, and the 3D model by the commercial CFD software is used for modelling the two-phase system and the particle motion in the fluid column. Settling velocity is calculated and compared to the velocity of a particle recorded by a high-speed camera measurement system in the laboratory scale sedimentation equipment. The results are promising, and after improvements, the simulator can be a useful tool in supporting energetically optimal industrial design and operation.